In the field of integrated circuit packaging, it is known to include a plurality of integrated circuits in a single package body. Providing a plurality of integrated circuits in one package allows an increase in package density without a significant increase in the area of the printed circuit board that is consumed by the package.
A problem with conventional packages, even packages that contain a plurality of integrated circuits, is that further increases in density per unit area of the printed circuit board are not easily attainable. So, for example, if a package includes two sixteen megabit memory integrated circuits (total thirty-two megabits), then increasing the total amount of memory to 128 megabits would require three additional packages, each of which would require additional mounting area on the printed circuit board. Artisans have attempted to stack separate packages on top of each other to avoid increases in mounting area, but such stacking methods can be difficult and time consuming.
The present invention includes an integrated circuit package that may be easily stacked upon another similarly-constructed package so as to form an electrical and physical connection with the other package. The stacked packages may contain the same or different types of integrated circuits. For example, two memory packages may be stacked or a memory package may be stacked with a microprocessor package. The package design provides the user with flexibility in deciding how many and what types of packages to stack.
One embodiment of the present invention includes a substrate for making an integrated circuit package. The substrate includes a molded plastic body having an integrated circuit mounting region and a plurality of integral plastic posts extending vertically from body. The posts may include first posts extending from a first side of the body and second posts extending from an opposite second side. The posts are coated with metal. The body also includes electrically conductive paths, which may include metal traces on the body and metal vias through the body, that are electrically connected to the metal coating of the posts.
The present invention also includes a method of making an integrated circuit package using the above substrate, and the integrated circuit package made thereby. An integrated circuit (e.g., a memory, microprocessor, or optical chip, or a micromachine) is mounted in the chip mounting region of the substrate. The integrated circuit is electrically connected to the metal coating of the posts through the electrically conductive paths of the substrate. For example, in an embodiment where first and second posts are provided on opposing sides of the package body, an integrated circuit mounted on the first side of the body may be electrically connected by bond wires to metal traces on the first side of the body, which traces are electrically connected to the metal coatings of the first posts and to vias through the body that are electrically connected to the metal coatings of the second posts.
Another embodiment of the present invention includes a stack of integrated circuit packages. The stack includes at least two of the above-described packages one on top of the other. The posts of one package are engaged with the posts of the other package so that their respective metal coatings contact each other, thereby forming an electrical connection between the packages.
The present invention also includes a method of stacking the above-described packages. In one embodiment, the method includes inserting each second post of one of the packages into a space between a group of first posts of another package so that each second post is physically connected to the respective group of first posts and is electrically connected to at least some of the first posts of the respective group.
Another embodiment of the present invention includes a method for making the above described substrate. The method includes molding a plastic package body having vertically extending plastic posts. The posts are then coated with metal. Vias may be formed through the substrate, by, for example, drilling holes through the body and filling the holes with metal. Metal traces also are formed on the body and are electrically connected to the vias and the metal coatings on the posts.
Another embodiment of the present invention includes a mounting substrate upon which the above-described integrated circuit packages may be easily mounted. The mounting substrate includes a molded plastic sheet having a plurality of integral plastic posts extending vertically from at least one side of the sheet. All or some of the posts are coated with metal. The posts are arranged in groups, with each group including a plurality of posts. A space is between the posts of each group. The posts are sized and arranged so that a metal-coated post of an integrated circuit package may be inserted snugly into the space between the posts of some of the groups of posts on the mounting substrate, thereby forming an electrical connection through contact between the metal coatings of the respective posts. An electrically conductive connector (e.g., an edge connector) is included on the mounting substrate. At least some of the groups of posts of the mounting substrate are electrically connected to the connector, which allows the integrated circuit packages mounted on the mounting substrate to be electrically connected to external circuitry.
These embodiments and other aspects of the present invention will be further described in the detailed description below and in the accompanying figures.